These are the steps I would follow to configure NAT (Network Address Translation) on a Cisco 1921 Router. The tool of choice is Putty configured to log the commands. You could use the Cisco IOS context Help to assist with the configuration:

1) Open the Putty application and select the Serial Port Connection Type to logon locally to the router device. Edit the Com port number to your settings and click Open. I’m using a Serial-to-USB adapter with the Router Console cable.

2) You will be prompted to enter the initial configuration mode. Type no and enter.

3) To effect the initial configuration of the router, enter privileged mode, then the configuration mode. Configure the Router name, the enable secret password, and service password-encryption(this command encrypts all passwords) . Still in config mode,enter the line console mode and enable the logging synchronous function: